Subsea telescoping and rotatable sub

ABSTRACT

A subsea telescoping and rotatable connector or sub is coupled into a riser. The sub includes two coupled bodies that are both axially and rotatably moveable relative to each other such that the sub enables the riser to move axially in response to tension or compression in the riser and rotate in response to surface vessel rotation or other torques. The sub expands and contracts in response to the tension or compression in the riser, and swivels in response to surface vessel rotation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to copending and commonly assigned patentapplication entitled “MARINE SUBSEA RISER SYSTEMS AND METHODS”, AttorneyDocket No. 500005, filed contemporaneously herewith and incorporatedherein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND

The present disclosure relates in general to systems and methods usefulin marine hydrocarbon exploration, production, well drilling, wellcompletion, well intervention, and containment and disposal fields.During offshore operations, a riser system couples the ship at the seasurface to the sea bed along with the subsea drilled earthen boreholefor recovering hydrocarbons. Riser systems have been used duringdrilling, production/injection, completion/workover, and exportoperations. A drilling riser can be deployed below a drill ship,commonly known as a mobile offshore drilling unit (MODU). The drillingriser connects at the seabed to a wellhead, generally, and, morespecifically, to a lower marine riser package (LMRP) and blow outpreventer (BOP). For well control and intervention situations, and forwells completed with vertical subsea trees, a Completion Workover Riser(CWOR) system may be used. To produce and/or contain hydrocarbons from awell, a production riser system may be used, includingquick-connect/disconnect systems.

In any of the various systems mentioned above, the riser connectionbetween a subsea source and a surface vessel will be exposed to theforces of the surrounding sea. For example, sea currents may actdirectly upon the riser. Likewise, sea surface motion can cause thesurface vessel to move relative to the stationary wellhead where theriser is connected subsea. The draft of the vessel will change ashydrocarbons are stored aboard the vessel, causing longitudinal motionof the riser. The movements and forces caused by these actions, such asbuckling or torque, can create stresses in the riser.

Accordingly, there remains a need for a riser connector or sub that canaccommodate the movements and forces acting upon the riser whilepreventing the stresses to the riser. More particularly, there remains aneed for a riser connector or sub that can accommodate variousdirections or kinds of movements, such as longitudinal, or axial, androtational, while maintaining a substantially stress-free connectionbetween the subsea source and the surface vessel.

SUMMARY

A riser connector includes two bodies coupled such that the two bodiesexhibit longitudinal, or axial, movement and rotational movementrelative to each other. The connector may include a sub having a firsttubular body telescopically received within a second tubular body. Thetubular bodies are axially moveable relative to each other. The tubularbodies are rotationally moveable relative to each other. The couplingbetween the tubular bodies includes a series of chambers, bores, ports,flowpaths, and radial, cross-sectional areas that interact to provideaxial and rotational movement within the sub while being connected intoa riser system disposed in a subsea environment. In some embodiments,the coupling between the tubular bodies is not influenced by a pressuredifference between a fluid internal to the sub and a fluid external tothe sub.

In certain embodiments, a subsea riser connector includes a first bodytelescopically received within a second body, an inner flow bore throughthe first and second bodies, a chamber disposed between the first andsecond bodies, a sliding seal disposed in the chamber and slidinglyengaged with the first and second bodies, and a cylindrical interfacebetween the first body and the second body to enable relative axialmovement and relative rotational movement between the first and secondbodies. The sliding seal may separate the chamber into a first chamberportion and a second chamber portion. The first chamber portion mayinclude a port in fluid communication with the inner flow bore. Thesecond chamber portion may include a port in fluid communication with anexterior of the first and second bodies. An effective area Ai at an endof the first body disposed in a flow bore of the second body may receivea pressure Pi in the inner flow bore. An annular area AA in the firstchamber portion may receive the pressure Pi from the inner flow bore.The effective area Ai may be substantially equal to the annular area AA.The annular area AA may be greater than the effective area Ai. The firstchamber portion may include a stop. The second chamber portion mayinclude a stop. The first chamber portion may include a biasing spring.

In some embodiments, the first chamber portion includes a port having aone-way valve disposed between the first chamber portion and an exteriorof the first and second bodies. The second chamber portion may include aport in fluid communication with the exterior of the first and secondbodies. An effective area Ai at an end of the first body disposed in aflow bore of the second body may receive a pressure Pi in the inner flowbore. The one-way valve may be configured to communicate a pressurizedfluid to the first chamber portion and bias the connector.

In some embodiments, the cylindrical interface may include a firstcylindrical surface at an end of the first body mating with a secondcylindrical surface in a flow bore of the second body. A sliding sealmay be disposed between the first and second cylindrical surfaces. Thefirst cylindrical surface may be axially moveable and rotatable relativeto the mating second cylindrical surface. The cylindrical interface mayinclude a third cylindrical surface on the first body opposite thechamber from the first cylindrical surface, with the third cylindricalsurface mating with a fourth cylindrical surface in the second bodyopposite the chamber from the second cylindrical surface. The thirdcylindrical surface may be axially moveable and rotatable relative tothe mating fourth cylindrical surface.

In some embodiments, a subsea riser system includes a first bodytelescopically received within a second body, a riser coupled to thefirst and second bodies, an inner flow bore through the first and secondbodies, the inner flow bore in fluid communication with an inner flowbore of the riser, a chamber disposed between the first and secondbodies, a sliding seal disposed in the chamber and slidingly engagedwith the first and second bodies, and a cylindrical interface betweenthe first body and the second body to enable relative axial movement andrelative rotational movement between the first and second bodies. Abiasing force may be included in the chamber to put the riser intension. The cylindrical interface may include a plurality of matingcylindrical surfaces between the first and second bodies wherein eachmating cylindrical surface is axially moveable and rotatable relative toan opposing mating cylindrical surface.

A method of connecting to a subsea riser includes telescopicallyreceiving a first body within a second body, coupling the first andsecond bodies to a subsea riser, axially moving the first and secondbodies relative to each other at a cylindrical interface disposedbetween the first and second bodies in response to a tension orcompression force on the riser, and rotationally moving the first andsecond bodies relative to each other at the cylindrical interface inresponse to a torque on the riser. The method may further includecommunicating a fluid through an inner flow bore of the first and secondbodies. The method may further include communicating the fluid to afirst chamber portion of a chamber between the first and second bodies.The method may include pressure balancing the first and second bodies inresponse to communicating the fluid to the first chamber portion. Themethod may include communicating an exterior fluid to a second chamberportion of the chamber. The cylindrical interface may include multiplesets of mating surfaces, and the method may further include axiallymoving and rotationally moving each set of mating surfaces. The methodmay include biasing the first and second bodies toward each other toplace the subsea riser in tension.

Thus, embodiments described herein include a combination of features andadvantages intended to address various shortcomings associated withcertain prior devices, systems, and methods. The various characteristicsdescribed above, as well as other features, will be readily apparent tothose skilled in the art upon reading the following detaileddescription, and by referring to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of exemplary embodiments of the invention,reference will now be made to the accompanying drawings in which:

FIG. 1 is a schematic view of an embodiment of an offshore drilling orproduction riser system;

FIG. 2 is a longitudinal cross-section view of a subsea telescoping androtatable sub that can be coupled into the riser of FIG. 1, inaccordance with the principles disclosed herein;

FIG. 3 is an elevational view of an inner mandrel of the sub of FIG. 2;

FIG. 4 is a perspective view of the sub of FIG. 2;

FIG. 5 is a partial cross-section view of another embodiment of thesubsea telescoping and rotatable sub of FIG. 2;

FIG. 6 is a partial cross-section view of yet another embodiment of thesubsea telescoping and rotatable sub of FIG. 2;

FIG. 7 is a partial cross-section view of a further embodiment of thesubsea telescoping and rotatable sub of FIG. 2; and

FIG. 8 is a partial cross-section view of a dual or hybrid chamberembodiment of the subsea telescoping and rotatable sub of FIG. 2.

DETAILED DESCRIPTION

In the drawings and description that follow, like parts are typicallymarked throughout the specification and drawings with the same referencenumerals, respectively. Certain terms are used throughout thedescription and claims to refer to particular features or components. Asone skilled in the art will appreciate, different persons may refer tothe same feature or component by different names. This document does notintend to distinguish between components or features that differ in namebut not function. The drawing figures are not necessarily to scale.Certain features and components may be shown exaggerated in scale or insomewhat schematic form and some details of conventional elements maynot be shown in the interest of clarity and conciseness. The presentinvention is susceptible to embodiments of different forms. Specificembodiments are described in detail and are shown in the drawings, withthe understanding that the present disclosure is to be considered anexemplification of the principles of the invention, and is not intendedto limit the invention to that illustrated and described herein. It isto be fully recognized that the different teachings of the embodimentsdiscussed below may be employed separately or in any suitablecombination to produce desired results.

The terms “including” and “comprising” are used in an open-endedfashion, and thus should be interpreted to mean “including, but notlimited to . . . .” Unless otherwise specified, any use of any form ofthe terms “couple”, “attach”, “connect” or any other term describing aninteraction between elements is not meant to limit the interaction todirect interaction between the elements and may also include indirectinteraction between the elements described. Thus, if a first devicecouples to a second device, that connection may be through a directconnection, or through an indirect connection via other devices,components, and connections. In addition, as used herein, the terms“axial” and “axially” generally mean along or parallel to a central axis(e.g., central axis of a body or a port), while the terms “radial” and“radially” generally mean perpendicular to the central axis. Forinstance, an axial distance refers to a distance measured along orparallel to the central axis, and a radial distance means a distancemeasured perpendicular to the central axis. A “subsea source” includesany subsea location where hydrocarbons are produced, communicated, orcontained.

Referring initially to FIG. 1, an embodiment is illustratedschematically of an offshore system 100 for deepwater subseacontainment, disposal, production, and well intervention. While many ofthe apparatus, systems, and methods described herein were developed andused in the context of containment and disposal, it is explicitly notedthat the apparatus, systems, and methods described herein are notrestricted to containment and disposal operations, but may be used indrilling or in conjunction with any subsea source.

The system 100 includes a lower riser assembly or LRA 4 including awellhead housing 2. In some embodiments, the wellhead housing 2 is asubstantially cylindrical member. In certain embodiments, the wellheadhousing 2 may be configured for or include components for otheroperations as noted above. The wellhead housing 2 may include or becoupled to a BOP for drilling operations. The wellhead housing 2includes one or more male/female subsea connectors 26 used for couplingto various subsea equipment related to the riser systems and otheroperational systems noted herein. On some embodiments, the wellhead 2and the connectors 26 may be part of a Christmas tree arrangement as isknown in the industry. The wellhead 2 is affixed to a bottom plate 96,for example, by welding or bolting. The bottom plate 96 is in turnattached by welding, bolting, or some other mechanism to a seabedfoundation 54, which may be any solid foundation. The seabed foundationmay surround or otherwise be adjacent an earthen drilled borehole 8 forproducing hydrocarbons.

The wellhead housing 2 fluidly and mechanically couples to a lower riserportion or tubular string 6 of a riser 10. The riser 10 may include aseries of connected tubulars, such as drill pipe sections or joints. Theriser may also include other subsea tubulars for coupling the subseasource to a surface vessel 28. In certain system embodiments the riserjoints may be constructed using high strength steel tubulars usingthreaded coupled connectors. The riser 10 includes an upper riserportion 24 to fluidly and mechanically couple with the vessel 28 in aknown fashion. During installation from the surface vessel 28 at seasurface 50, certain known apparatus may be used to help guide the riser10 and the lower riser portion 6 into a connection with the wellhead 2.Once connected, the riser 10 may experience stresses due the movementsand forces of the sea imposed upon the system 100 as previouslydescribed. In certain embodiments, a telescoping and rotatable connectoror sub 20 is coupled into the riser 10 to accommodate these imposedmovements and forces and to reduce the stresses in the riser 10.

For ease of description, the telescoping and rotatable connector or sub20 may also be referred to simply as connector 20 or sub 20. The sub 20generally includes a head or first tubular body 22 including atelescoping section or inner mandrel 21 received within a housing orsecond tubular body 60. The head 22 is rotatable relative to the housing60 and may swivel in response to rotation of the surface vessel 28. Thehead 22 is also axially (i.e., the direction of the longitudinal axis ofthe riser 10 between the wellhead 2 and the vessel 28) moveable relativeto the housing 60 such that the sub 20 is expandable and contractible.The connection or coupling between the inner mandrel 21 and the housing60 is configured to absorb these movements, as will be described ingreater detail below.

Referring now to FIG. 2, a longitudinal cross-section view of the sub 20illustrates further details of the telescoping and rotatable aspects ofthe sub 20. For simplicity and ease of description, certain details ofthe sub 20 are not shown. For example, connections required for assemblyand disassembly of the sub 20 are not shown. The sub 20 includes thefirst tubular body 22, or the head, received within the second tubularbody 60, or the housing. The coupled first body 22 and the housing 60include a shared longitudinal axis 25. The first body 22 includes an end30 having an outer surface 35 with an outer diameter 34. At a shoulder32, the first body 22 is reduced in diameter to an outer surface 40 ofthe inner mandrel 21. At an intermediate location on the inner mandrel21, the outer surface 40 transitions to an increased diameter portion 42and then to a reduced outer diameter surface 46 that terminates at anend 48 of the inner mandrel 21. The reduced outer surface 46 includes adiameter 49. The inner mandrel 21 includes an inner bore 36 having aninner surface diameter 38.

The housing 60 includes a first end 62, a second end 64, and an outersurface 65 having the outer diameter 34 extending between the ends 62,64. An inner surface 66 at the second end 64 contacts and slidinglyengages the mandrel surface 40 as shown and together define an interfacetherebetween. Accordingly, the inner surface 66 is substantially thesame diameter 67 as the surface 40. The inner surface 66 transitions toan increased diameter surface 74 at a shoulder 68. The surface 74extends to another shoulder 76 to form a chamber 70 with the outersurfaces 40, 42, 46 of the inner mandrel 21. A seal 44, such as ano-ring shaped sliding seal, for example, is disposed about the increaseddiameter portion 42 and slidingly engaged with the inner housing surface74. Thus, the increased diameter portion 42 (along with the remainder ofthe first body 22) and the inner housing surface (along with theremainder of the housing 60) are axially moveable along and rotatableabout the axis 25 relative to each other. In some embodiments, thesliding seal 44 is substantially stationary on the increased diameterportion 42, and thus is slidable along the inner housing surface 74 androtatable on the inner housing surface 74. In some embodiments, thefirst body 22 moves axially and/or rotates relative to the substantiallystationary housing 60. In other embodiments, the housing 60 movesaxially and/or rotates relative to the substantially stationary firstbody 22. In still other embodiments, there is combined axial and/orrotational movement of both the first body 22 and the housing 60.

The increased diameter portion 42 and the seal 44 separate the chamber70 into a first chamber portion 70 a and a second chamber portion 70 b.The inner mandrel 21 includes a first port 72 extending between theinner flow bore 36 and the outer surface 40 such that the first chamberportion 70 a is able to fluidly communicate with the inner flow bore 36.In some embodiments, the inner mandrel 21 includes additional ports 72between the inner flow bore 36 and the first chamber portion 70 a. Thehousing 60 includes a second port 78 and a third port 79 extendingbetween the surfaces 74, 65 such that the second chamber portion 70 b isable to fluidly communicate with the exterior of the sub 20, or thesurrounding sea water 29 at a pressure P_(s). In some embodiments, thehousing includes more or less than the two ports 78, 79.

Still referring to FIG. 2, the mandrel end 48 is disposed in a bore 84in the housing 60. The bore 84 includes an inner surface 80 that sharessubstantially the same diameter 49 as the outer mandrel surface 46 suchthat inner surface 80 contacts and slidingly engages the outer mandrelsurface 46 as shown and defines an interface therebetween. The bore 84transitions to a reduced diameter bore 86 at a tapered surface 82. Thereduced bore 86 includes the diameter 38 also shared with the inner flowbore 36 of the first body 22.

In some embodiments, in addition to the axially slidable and rotatablesliding seal 44, other sliding seals 88, 90 may be provided at thesurface interfaces 40, 66 and 46, 80 such that these interfaces aresealed while also promoting relative axial and rotational movementbetween the first body 22 and the housing 60. However, in someembodiments, other types of seals are located at 88, 90, or no seals areprovided though the relative axial and rotational movement at theinterfaces 40, 66 and 46, 80 remain to promote the movements in the sub20 as just described.

In operation, the sub 20 is coupled into a riser 10 of a subsea system100 as shown in FIG. 1. In some embodiments, the first body end 30 iscoupled to the upper riser portion 24 and the housing end 62 is coupledto the lower riser portion 6 using known means. In such an embodiment,the sub 20 is coupled into an intermediate location of the riser 10between upper 24 and lower 6 portions of the riser 10. In otherembodiments, the sub 20 may be coupled into a lower portion 6 of theriser 10, such that the first body end 30 is coupled to the riser 10 andthe housing end 62 is coupled to the wellhead 2, an attachment on thewellhead 2, or another component associated with the wellhead 2 or otherequipment at the subsea source. In some embodiments, the housing end 62is coupled to the upper riser portion 24 or the riser 10, and the firstbody end 30 is coupled to the lower riser portion 6 or the wellheadassociated equipment.

While coupled to the riser 10, a flow in either direction in the riser10 is received by a flow path 92 including the inner flow bores 36, 84,86. The fluid flow path 92 may direct hydrocarbon production from theborehole 8 and the subsea source to the surface vessel 28, or it maydirect an injection fluid flowing in the opposite direction. Other typesof flows are also contemplated according to the other systems describedherein. The fluid flow along the path 92 can include a pressure P_(i)that is communicated to and acts upon an effective area A_(i) at theradial terminal end 48 of the inner mandrel 21. Referring to FIG. 3, theeffective area A_(i) is shown extended across the radial plane of theend 48 and the inner flow bore 26, and includes the diameter 49. Thepressure P_(i) is also communicated to the first chamber portion 70 avia the port 72, and acts upon an annular area A_(A) that includes theradial or diameter difference between the mandrel surfaces 40 and theinner housing surface 74. The opposing chamber portion 70 b is atseawater or ambient pressure P_(s) via the ports 78, 79, thus thepressure P_(i) at A_(A) is opposed mainly by the pressure P_(i) at theeffective area A_(i). In some embodiments, P_(i)A_(i) is substantiallyequal to P_(i)A_(A) such that the sub 20 is pressure balanced across theincreased diameter portion 42, meaning there is substantially no biasingforce acting on the first body 22 and the housing 60 to push thesebodies toward or away from each other. In this manner, the increaseddiameter portion 42 also acts as a piston and may be referred to as thepiston 42 herein. In such embodiments, the effective internal area A_(i)is substantially equal to the annular chamber area A_(A). Accordingly,the first body 22 and the housing 60 can move axially, or telescope,relative to each other without being impeded by axial biasing forcescaused by the pressure P_(i) which would otherwise act to push thepiston 42 against the shoulder 68.

In some embodiments, the sub 20 may include additional “stages” toprovide additional areas for pressure balancing. For example, additionalpistons 42 with seals 44 can be disposed along the inner mandrel 21 toprovide further annular chamber area A_(A). In further embodiments, thesub 20 may include further effective areas for receiving the pressureP_(i).

In still further embodiments, the annular area A_(A) can be larger thanthe effective internal area A_(i). Assuming the pressure P_(i) continuesto act on the areas at A_(A), A_(i) as described above, then P_(i)A_(A)is greater than P_(i)A_(i). Consequently, a biasing force is provided inthe first chamber portion 70 a that contracts the sub 20 and enables atensioning force relative to the riser 10 into which the sub 20 iscoupled. Such a biasing or tensioning force in the sub 20 can counteractweights or forces of structures coupled below the sub 20.

While being pressure balanced as described, the sub 20 is able to expandand contract by virtue of axially slidable interfaces 46, 80 and 40, 66,along with the sliding seal 44. The surfaces 46, 80, 40, 66, 74 aremating circular or cylindrical surfaces that are free to slide relativeto each other, thus allowing relative axial movement between the firstbody 22 and the housing 60. Further, the cylindrical interface 46, 80,the cylindrical interface 40, 66, and the cylindrical interface betweenthe sliding seal 44 and the surface 74 enable the contacting surfaces torotate relative to each other. Accordingly, the first body 22 and thehousing 60 are free to rotate relative to each other, or swivel. Eachcylindrical interface between the inner mandrel 21 and the housing 60are configured for both axial and rotational movement, such that thereare no impedances to expansion/contraction and swiveling of the sub 20.

Referring now to FIG. 4, a perspective view of the sub 20 illustratesthe movements of the sub 20 from an exterior view. As previouslydescribed, the first body 22 is telescopically disposed in the housing60. One or more cylindrical surface interfaces are configured for dualaxial and rotational movement between the first body 22 and the housing60 of the sub 20. A cylindrical sealing interface provided between thechamber seal 44 and the housing surface 74 enables a dual axial androtational movement 110 between the first body 22 and the housing 60. Afirst cylindrical interface provided at surfaces 46, 80 enables anotherdual axial and rotational movement 112. A second cylindrical interfaceprovided at surfaces 40, 66 enables yet another dual axial androtational movement 108. Together, these interfaces provide a combinedcylindrical interface that aggregates the movements 108, 110, 112,resulting in axial movement or expansion/contraction of the sub 20 at102 and rotational movement or swiveling of the sub 20 at 104, 106.

Referring now to FIG. 5, a partial cross-section view of an alternativeembodiment of the sub 20 is shown. Many of the features shown in FIG. 5are similar to features shown in FIG. 2 for the sub 20. Consequently,common features between FIGS. 2 and 5 may not be described in detail inthe following discussion, though similarity between reference numeralsis maintained for ease of reference. The longitudinal cross-section viewof FIG. 5 depicts a sub 220 similar to the sub 20 of FIG. 2, but alsodifferent in certain respects. It is noted that only one half of the sub220 is shown, as taken about an axis 225.

The sub 220 includes a first body 222 with an inner mandrel 221 receivedwithin a housing 260. In some embodiments, the first body 222 includes aconnector or thread 223 and the housing 260 includes a connector orthread 261. The first body 222 includes a shoulder surface 232 facing ashoulder surface 264 of the housing 260. The shoulder surfaces 232, 264are separated by a gap or space 235. An increased diameter portion 242of the inner mandrel 221 separates a first chamber portion 270 a from asecond chamber portion 270 b, and is slidable along a surface 274 via asliding seal 244. The first chamber portion 270 a is exposed to aninternal pressure P_(i) via a port 272 and the second chamber portion270 b is exposed to an exterior or sea water pressure P_(s) via a port279. A shoulder 268 adjacent the first chamber portion 270 a is providedwith a step or stop 275. The stop 275 includes a first surface 273 and asecond surface 277. The increased diameter portion 242 includes a stepor stop 245 extending into the second chamber portion 270 b. The stop245 includes a first surface 243 and a second surface 247.

During operation of the sub 220, if the first body 222 and the housing260 are being forced away from each other such that the gap 235 isincreasing, the stop 275 may act as a stop against the increaseddiameter portion 242, or piston 242, before the piston 242 reaches theshoulder 268. If the piston 242 contacts the first surface 273 of thestop 275, a sub-chamber defined piston 242, the shoulder 268, and thesecond stop surface 277 remains to receive the pressure P_(i) andmaintain the pressure balancing effect as previously described. If thepiston 242 is allowed to fully contact and engage the shoulder 268, theport 272 may be completely sealed off from the first chamber portion 270a at a surface 266 and the pressure balancing effect may be lost. Thestop 275 prevents full contact between the piston 242 and the shoulder268.

Similarly, the stop 245 may engage a shoulder 276 of the second chamberportion 270 b. When the first body 222 and the housing 260 are movingtoward each other such that the gap 235 is decreasing, the first surface243 of the stop 245 can engage the shoulder 276 so that the piston 242is prevented from contacting the shoulder 276. Consequently, asub-chamber defined by the piston 242, the shoulder 276, and the secondstop surface 247 remains to receive the pressure P_(s) and maintain thepressure balancing effect as previously described. If the piston 242 isallowed to fully contact and engage the shoulder 276, the port 279 maybe completely sealed off from the second chamber portion 270 b by thepiston 242 and the pressure balancing effect may be lost. The stop 245prevents full contact between the piston 242 and the shoulder 276. Thecylindrical interfaces, as previously described with respect to the sub20 and which are included in the sub 220, continue to enable the sub 220to both telescope axially and rotate in response to riser forces.

Referring now to FIG. 6, a partial cross-section view of anotherembodiment of the subs 20, 220 is shown. As stated previously, commonfeatures with previous embodiments may not be shown or described in theinterest of clarity and simplicity. Instead, the following discussionfocuses on different features of a sub 320 while attempting to maintainsimilarity between reference numerals used. The longitudinalcross-section view of FIG. 6 depicts the sub 320 similar to the subs 20,220, but also different in certain respects. It is noted that only onehalf of the sub 320 is shown, as taken about an axis 325.

The sub 320 includes a first body 322 with an inner mandrel 321 receivedwithin a housing 360. In some embodiments, the first body 322 includes aconnector or thread 323 and the housing 360 includes a connector orthread 361. The first body 322 includes a shoulder surface 332 facing ashoulder surface 364 of the housing 360. The shoulder surfaces 332, 364are separated by a gap or space 335. An increased diameter portion 342of the inner mandrel 321 separates a first chamber portion 370 a from asecond chamber portion 370 b, and is slidable along a surface 374 via asliding seal 344. The first chamber portion 370 a is exposed to aninternal pressure P_(i) via a port 372 and the second chamber portion370 b is exposed to an exterior or sea water pressure P_(s) via a port379. A shoulder 368 adjacent the first chamber portion 370 a is opposedto the increased diameter portion 342 to axially contain a biasingspring 395 in the first chamber portion 370 a.

During use of the sub 320, the biasing spring 395 provides an axialbiasing force in the first chamber portion 370 a that acts on theshoulder 368 and the increased diameter portion 342, or piston 342, topush the first body 322 and the housing 360 toward each other.Consequently, the gap 335 tends to decrease and the sub 320 tends tocontract if the biasing force is unopposed by other forces. During usein the riser 10, the biasing spring 395 enables a tensioning forcerelative to the riser 10 into which the sub 320 is coupled. Such abiasing or tensioning force in the sub 320 can counteract weights orforces of structures coupled below the sub 320. A series of slidingseals 344, 388, 390 and the associated, respective cylindrical surfacesas described herein enable the spring-biased sub 320 to both telescopeand rotate in response to forces applied to the sub 320.

In a further embodiment, and referring to FIG. 7, a sub 420 replaces thebiasing spring 395 with a gas spring or gas chamber 489 in a firstchamber portion 470 a. A valve 487 is coupled into a port 485 that is influid communication with the first chamber portion 470 a. A port in aninner mandrel 421, such as the ports 72, 272, 372, is no longer needed.In some embodiments, any one of the ports 72, 272, 372 is plugged. Insome embodiments, the valve 487 may be a one-way valve. In certainembodiments, the valve 487 may be a one-way valve stem, or a tire valvestem. In other embodiments, the valve 487 is a hand-operated valve, orother known two-way valves. The valve 487 may receive a pressurized gasor fluid and communicate the pressurized gas to the spring or chamber489 while also preventing the pressurized gas from escaping.Consequently, a biasing force is provided in the first chamber portion470 a similar to the biasing force provided by the biasing spring 395.In some embodiments, a second chamber portion 470 b is in fluidcommunication with the exterior sea water and a pressure P_(s) via aport 479. In other embodiments, the port 479 is plugged or closed, or iseliminated, and the second chamber portion 470 b includes or ismaintained at atmospheric pressure. Such an atmospheric pressure chamberportion can also be seen in FIG. 8 and discussed below.

Referring now to FIG. 8, an alternative embodiment sub 520 includes ahybrid or stacked arrangement of multiple pressurized chambers, eachpressurized chamber similar to ones included with other embodimentsdescribed herein. The sub 520 includes a first set of chamber portions570 a, 570 b similar to the chamber portions 470 a, 470 b of the sub 420of FIG. 7. The chamber portions 570 a, 570 b include related structuresand features similar to the chamber portions 470 a, 470 b of the sub420, wherein similar reference numerals are used to denote similarfeatures. For example, the piston 442 in FIG. 7 is the same as a piston542 of the sub 520 in FIG. 8. Thus, particular reference can be made toFIG. 7 and associated text for additional details of the sub 520,including for a first body 522 and a housing 560. However, one featureis different. Instead of having the port 479, the housing 560 of the sub520 does not include the port 479 and instead the chamber portion 570 bis an atmospheric chamber as discussed above with respect to theadditional embodiments for the sub 420 of FIG. 7.

The sub 520 also includes a second pressurized chamber disposed axiallyadjacent the first set of chamber portions 570 a, 570 b. A second set ofchamber portions 670 a, 670 b similar to the chamber portions 270 a, 270b of the sub 220 of FIG. 5 are coupled or attached to a shoulder area568 and what was the surface 464 in FIG. 7. The chamber portions 670 a,670 b include related structures and features similar to the chamberportions 270 a, 270 b of the sub 220, wherein similar reference numeralsare used to denote similar features. For example, the piston 242 in FIG.5 is the same as a piston 642 of the sub 520 in FIG. 8. Thus, particularreference can be made to FIG. 5 and associated text for additionaldetails of the chamber portions 670 a, 670 b of the sub 520.Consequently, the housing 560 includes dual, or stacked, pressurizedchambers in the form of chamber portions 570 a, 570 b and chamberportions 670 a, 670 b. Further, the sub 520 includes the first piston542 and the second piston 642.

During use, the chamber portions 670 a, 670 b enable the pressurebalancing function as described for the sub 220 of FIG. 5. Further, thechamber portions 570 a, 570 b enable the pressurized gas biasingfunction as described for the sub 420 of FIG. 7. In alternativeembodiments, the chamber portions 570 a, 570 b can be replaced with thechamber portions 370 a, 370 b and the biasing spring 395 of FIG. 6 toenable a spring-based biasing force in the sub 520. In this manner, asingle sub 520 can be equipped with stacked chambers that enable thepressure balancing function of the sub 220 of FIG. 5 and the biasingforce function of any one of the subs 220, 320, 420 of FIGS. 5, 6, and7, respectively.

Described herein are riser systems connecting a subsea source to asurface vessel, which may be a drill ship such as a MODU or other vesselincluding a drilling rig. Certain embodiments include a near-verticalriser having a lower end and an upper end, the upper end of the risermechanically and fluidly connected to the surface vessel. Certainembodiments described herein include a telescopically rotatableconnector or sub disposed in an intermediate portion of the riserbetween the lower and upper ends, or at a lower end of the riser andconnectable to wellhead equipment. The telescopically rotatable subincludes an inner cylindrical interface that facilitates both relativeaxial movement and relative rotational movement between twotelescopically received tubular bodies of the sub. The inner cylindricalinterface may include multiple sets of mating seals and surfaces ormating surfaces, all of which are configured for axial relative movementand rotational relative movement. The two bodies may include a chamberbetween them, with a sliding seal disposed therein and engaging both ofthe bodies. The divided chamber can be pressurized so as to pressurebalance the two tubular bodies of the sub. Consequently, the axial androtational movements of the sub in response to subsea forces areunimpeded by pressure biasing forces in the sub.

While specific embodiments have been shown and described, modificationscan be made by one skilled in the art without departing from the scopeor teachings herein. The embodiments as described are exemplary only andare not limiting. Many variations and modifications of the systems,apparatus, and processes described herein are possible and are withinthe scope of the invention. For example, the relative dimensions ofvarious parts, the materials from which the various parts are made, andother parameters can be varied. Accordingly, the scope of protection isnot limited to the embodiments described, but is only limited by theclaims that follow, the scope of which shall include all equivalents ofthe subject matter of the claims.

What is claimed is:
 1. A subsea riser connector comprising: a first body telescopically received within a second body; an inner flow bore through the first and second bodies; a chamber disposed between the first and second bodies; a sliding seal disposed in the chamber and slidingly engaged with the first and second bodies; and a cylindrical interface between the first body and the second body to enable relative axial movement and relative rotational movement between the first and second bodies.
 2. The connector of claim 1, wherein the sliding seal separates the chamber into a first chamber portion and a second chamber portion.
 3. The connector of claim 2, wherein the first chamber portion includes a port in fluid communication with the inner flow bore.
 4. The connector of claim 3, wherein the second chamber portion includes a port in fluid communication with an exterior of the first and second bodies.
 5. The connector of claim 3, wherein an effective area A_(i) at an end of the first body disposed in a flow bore of the second body receives a pressure P_(i) in the inner flow bore.
 6. The connector of claim 5, wherein an annular area A_(A) in the first chamber portion receives the pressure P_(i) from the inner flow bore.
 7. The connector of claim 6, wherein the effective area A_(i) is substantially equal to the annular area A_(A).
 8. The connector of claim 6, wherein the annular area A_(A) is greater than the effective area
 9. The connector of claim 6, wherein the first chamber portion includes a stop.
 10. The connector of claim 6, wherein the second chamber portion includes a stop.
 11. The connector of claim 6, wherein the first chamber portion includes a biasing spring.
 12. The connector of claim 2, wherein the first chamber portion includes a port having a one-way valve disposed between the first chamber portion and an exterior of the first and second bodies, wherein the second chamber portion includes a port in fluid communication with the exterior of the first and second bodies, wherein an effective area A_(i) at an end of the first body disposed in a flow bore of the second body receives a pressure P_(i) in the inner flow bore, and wherein the one-way valve is configured to communicate a pressurized fluid to the first chamber portion and bias the connector.
 13. The connector of claim 1, wherein the cylindrical interface further comprises a first cylindrical surface at an end of the first body mating with a second cylindrical surface in a flow bore of the second body.
 14. The connector of claim 13, further comprising a sliding seal disposed between the first and second cylindrical surfaces.
 15. The connector of claim 13, wherein the first cylindrical surface is axially moveable and rotatable relative to the mating second cylindrical surface.
 16. The connector of claim 13, wherein the cylindrical interface further comprises a third cylindrical surface on the first body opposite the chamber from the first cylindrical surface, the third cylindrical surface mating with a fourth cylindrical surface in the second body opposite the chamber from the second cylindrical surface.
 17. The connector of claim 16, wherein the third cylindrical surface is axially moveable and rotatable relative to the mating fourth cylindrical surface.
 18. A subsea riser system comprising: a first body telescopically received within a second body; a riser coupled to the first and second bodies; an inner flow bore through the first and second bodies, the inner flow bore in fluid communication with an inner flow bore of the riser; a chamber disposed between the first and second bodies; a sliding seal disposed in the chamber and slidingly engaged with the first and second bodies; and a cylindrical interface between the first body and the second body to enable relative axial movement and relative rotational movement between the first and second bodies.
 19. The riser system of claim 18, further comprising a biasing force in the chamber to put the riser in tension.
 20. The riser system of claim 18, wherein the cylindrical interface further comprises a plurality of mating cylindrical surfaces between the first and second bodies wherein each mating cylindrical surface is axially moveable and rotatable relative to an opposing mating cylindrical surface.
 21. A method of connecting to a subsea riser comprising: telescopically receiving a first body within a second body; coupling the first and second bodies to a subsea riser; axially moving the first and second bodies relative to each other at a cylindrical interface disposed between the first and second bodies in response to a tension or compression force on the riser; and rotationally moving the first and second bodies relative to each other at the cylindrical interface in response to a torque on the riser.
 22. The method of claim 21, further comprising communicating a fluid through an inner flow bore of the first and second bodies.
 23. The method of claim 22, further comprising communicating the fluid to a first chamber portion of a chamber between the first and second bodies.
 24. The method of claim 23, further comprising pressure balancing the first and second bodies in response to communicating the fluid to the first chamber portion.
 25. The method of claim 23, further comprising communicating an exterior fluid to a second chamber portion of the chamber.
 26. The method of claim 21, wherein the cylindrical interface includes multiple sets of mating surfaces, and axially moving and rotationally moving each set of mating surfaces.
 27. The method of claim 22, further comprising biasing the first and second bodies toward each other to place the subsea riser in tension. 